Blade construction for a vane ring for turboengines

ABSTRACT

THE BLADE PART WHICH CONTACTS THE WORKING MEDIUM OF THE ENGINE IS MADE OF DIFFERENT MATERIALS FROM THE THE AXLE JOURNAL IN ORDER TO OPERATE EFFICIENTLY AT HIGH THERMAL LOADS. THE WORKING MEDIUM CONTACTING PART CAN EITHER BE FORCE-FIT OR SHRUNK-FIT IN THE JOURNAL OR UNITED WITH THE JOURNAL BY COMPOUND CASTING.

Jan. 5, v F ZERLAUTHI BLADE CONSTRUCTION FOR A VANE RING FOR TURBQENGINES' Filed Nov. 27, 1968 GSheets-Sheet 1 lnventur FEQD/NAND ZELPLHUTH BLADE CONSTRUCTION FOR A VANE RING FOR TURBOENGINES Filed Nov. 2'7, 1968 6 Sheets-Sheet 2 In ventor FERD/NHND zERmL/TH' ,qTTOQzE v5 Jan. 5,1971 F. Z'ERLAUTH 3,552,882

BLADE CONSTRUCTION FOR A VANE RING FOR TURBOENGINES Filed Nov. 27, 1968 v 6 Sheets-Sheet 5 Inventor FERD/N/QND ZERLQUT W 2/ 7 AWZZ Zm Jan. 5, 1971 F. .ZERLAUTH 3,552,882

BLADE CONSTRUCTION FOR A VANE RING FOR TURBOENGINES Filed Nov. 27, 1968 e Sheeis-Sheet 4 In ventor FERDINAND ZEQLHUTH F. ZERLAUTH Jan. 5, 1971 BLADE CONSTRUCTION FOR A VANE RING FOR TURBOENGINES 6 Sheets-Sheet 5 Filed Nov. 27, 1 968 A a. ml liliilillnlii Inventor: FERD/NFIND ZERLQUTH Jan. 5, 1971 F. ZERLAUTH 3,552,882

BLADE CONSTRUCTION FOR A VANE RING FDR TURBOENGINES Filed Nov. 27, 1968 6 Sheets-Sheet 6 In venfor FEPD/NQND Z ER LFIUTH United States Patent US. Cl. 416-241 3 Claims ABSTRACT OF THE DISCLOSURE The blade part which contacts the working medium of the engine is made of different materials from the axle journal in order to operate efficiently at high thermal loads. The working medium contacting part can either be force-fit or shrunk-fit in the journal or united with the journal by compound casting.

This invention relates to a blade construction for a vane ring for turboengines.

Turboengines have been known to utilize vane rings which have blades mounted therein in a manner so as to be adjusted angularly with respect to the plane of the vane ring. Usually, these blades have been rotatably mounted in the vane ring for rotation about their longitudinal axes. Turboengines of this type achieve substantial advantages as long as they are operated with low temperature working media. However, with elevated temperatures which produce service stresses it has been difficult to satisfy the conditions for perfect support of the blades and the conditions for high thermal loads simultaneously.

Accordingly, it is an object of the invention to provide a blade for high-temperature usage in a turboengine.

It is another object of the invention to form the parts of a turboengine blade of different materials suited to -the stress requirements of each part.

-an axle journal rotatably supporting the blade in a bearing housing. That is, the blade part which is to contact the working medium is made of a heat resistant material while the axle journal is made of a material suitable for dry'operation without any particular supply of lubricant in a bearing, for example, a heat resistant plastic bearing.

In order to join the parts of the blade together, the axle journal is made as a hollow cylindrical body and the blade part contacting the working medium is made with a blade journal at one end which is forced into or shrunk into the axle journal by undercooling. In another embodiment, the axle journal can be provided with a cylindrical bore and heat shrunk on a cylindrical blade journal.

In still another embodiment, the blade can be made 'as a compound casting with the part contacted by the work medium consisting of a heat resistant material and the axle journal part of the shaft consisting of a material suitable for dry operation in a heat resistant plastic bearing without a special supply. of lubricant.

The blade can also be provided with a neck between the part contacted by the work medium and the part acting as the axle journal which serves to remove heat by means of a heat transfer with a cooling medium. Such "ice a neck can be provided with cooling ribs which are in turn surrounded by a cylindrical bushing. Further, in this case, the cooling ribs are provided with alternatingly aranged passage ducts for the cooling medium so that the cooling medium between each two adjacent ribs is caused to flow tangentially at least around half the neck before reaching the next interspace between the ribs via the subsequent passage duct. The bushing surrounding the cooling ribs can be inserted in the blade carrier for the blade with a clearance and be pressed axially by means of a spring against a collar in such a way that the sleeve is centered with respect to the cooling ribs.

In order to reduce the cross-section of the heat flow from the blade part contacting the working medium in a direction toward the axle journal, the blade section outside this part, for instance, the blade neck or the blade journal adjoining thereto, or the blade neck and the blade journal, is preferably provided at least in part with an axial bore.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawing in which:

FIG. 1 illustrates a fragmentary cross-sectional view of a vane ring incorporating a blade according to the invention taken on line II of FIGS. 2 to 4;

FIG. 2 illustrates a view taken on line II-II of FIG. 1;

FIG. 3 illustrates a view taken in the plane of line IIIIII of FIG. 1 of two adjacent axle housings;

FIG. 4 illustrates a view taken on line IV-IV of FIG. 1;

FIG. 5 illustrates a cross-sectional View of a modified blade design and coolant passageway according to the invention; and

FIG. 6 illustrates a modified connection between adjacent axle housings for the coolant flow.

Referring to FIG. 1, the vane ring includes an annular blade carrier 1 and a plurality of blades, for example, twenty-eight, which are circumferentially spaced and carried on the blade carrier 1 substantially radially of the rotor shaft (not shown) in the ring plane IIIIII. The blade carrier 1 is formed with a bore 2 for each blade as well as with a recess 3 about the bore 2 for receiving an axle housing 4 of a bearing mount.

Each blade is formed with" a part 5 which contacts the working medium, a neck 6 substantially within the plane of the blade carrier 1, a blade journal '7 and an axle journal 8 secured about the blade journal 7. The part 5 merges into the neck 6 at the lower end while the neck 6 which is provided with cooling ribs 23 merges into the blade journal 7 to form a one-piece blade. This blade is further either forced into the journal 8 or is shrunk on by undercooling in order to form a unitary multi-part blade construction. The blade parts 5, 6, 7, are made of a material which is heat resistant to the heat generated in the working medium, for example, a heat resistant steel, whereas the axle journal 8 is made of a material, particularly at the bearing surfaces, having suitable dry operation properties. That is, the axle journal 8 is of a material capable of sliding without wear and without a special supply of lubricant on a plastic bearing. Thus, while the blade part 5 is able to resist the heat developed in the engine, the axle journal 8 is able to operate in a dry condition without damaging the bearings or itself.

3 supports 12, 13 while forming an open hollow space 14 and a closed hollow space 'between the walls 9, The open hollow space 14 is situated at a point closer to the blade carrier 1 than the closed hollow space 15 while being in facing relation to the blade carrier 1.

Referring to *FIGS. 2 and 3, the closed hollow spaces 15 of at least one group of axle housings 4 are interconnected by means of pipes 17 and together constitute a distribution line 16 which supplies each one of the connected axle housings 4 with a partial amount of a gaseous coolant, for instance, air. To this end, at least one of the housings 4 connected to the distribution line 16 is further connected with a supply line 19 (FIG. 2) which provides the total amount of gas required for the cooling of all the housings 4 connected to the distribution line 16. Alternatively, two supply pipes can be attached to the lower half of the blade carrier and connected to the two axle housings 4 next to their respective axial separating planes. Following joining of the lower and upper half of the blade carrier and installation of the connecting pipes 17, an inherently closed distribution line 16 is produced with two substantially diametrically opposite supply connections. During inspection and cleaning operations of the vane rings, the supply lines need not be removed.

Referring to FIG. 1, the open hollow space 14 and the closed hollow space 15 which forms a part of the distribution conduit 16 in each housing are interconnected by means of bores 18. These bores 18 allow the partial amount of the cooling gas required for each axle housing 4 to be branched off from the distribution line 16 to the individual cooling sites. Another portion of the cooling air is guided through the boring 55 to the space 56 between the casing of the blade carrier 1 and the ring segment 33 in order to protect the blade carrier 1 from excessive temperatures.

Referring to FIGS. 1 and 4, a displacement body 36 of U-shaped cross-section and discontinuous length is mounted in the open space 14 in inverted manner to form a pair of narrow coolant flow passages with the walls 9, 20. The outer leg 37 of the body 36 is of greater length than the inner and rests on a plate 22 in the recess 3 of the blade carrier 1. Bores 38 are provided in the lower end of this outer leg to permit coolant flow towards the blade neck 6.

With regard to the bearings 10, 11 afiixed at both ends of the cylindrical bore formed by the inner wall 9, such are formed of a plastic capable of withstanding dry operation free of lubricants as well as elevated temperatures, for example, a plastic known as DU. Such plastics are able to withstand temperatures up to 200 C. and above without suffering any damage, and exhibit slide properties which do not make it necessary to provide for a special supply of lubricants.

Each axle housing 4 includes a peripheral flange 21 near the base of the outer wall 20 which facilitates tightening of the housing 4 against the blade carrier 1 and the plate 22 positioned therebetween. The flange 21 surrounds the axle housing 4 at a distance from the blade carrier 1 so as to minimize the transmission of heat from the blade carrier 1 to the axle housing 4.

Additionally, the opposite end of the axle housing 4 has a thrust bearing mounted between the axle journal 8 and the housing 4. The thrust bearing includes a rotor disk 24 secured to the journal 8, a pair of sliding disks 25 on opposite sides of the rotor disk 24, and a mounting plate 26 secured on the housing 4 over the disks 24, 25. A sealing ring 55 is further mounted in a groove of the disk 26 to prevent an escape of cooling gas out of the axle housing 4 along the journal 8 into the space surrounding the blade carrier 1.

A hub 27 of an adjustable lever 28 is keyed over the end of the journal 8 to sealingly engage the sealing ring and to clamp the rotor disk 24 and the sliding disks 25 together against a shoulder 29 of the axle journal 8 so 4 that the disks 24, 25 follow the rotational motions of the journal 8 and lever 28.

The cooling ribs 23 on the neck 6 of the blade are surrounded by a sleeve 30 mounted with a slight clearance within the plate 22. The sleeve 30 is compressed at one end by means of the spring 31 against a recess 32 of a ring segment 33 of the blade carrier 1 and is prevented from falling out of the plate 22 by means of a circlip 34 in a groove at the other end. On the other hand, the sleeve 30 is fitted tightly onto the cooling ribs 23 so as to be centered by the blade free of resistance in the plate 22. A plurality of bores 39 are provided in the sleeve 30 to communicate the opposite sides of the sleeve with each other. The cooling ribs 23 are provided with peripherally located milled sections 35 alternating from rib to rib by a semi-circumference which face each other in two groups. These milled sections 35 cooperate with the sleeve 30 to define spaced passage ducts through which the cooling air can flow.

In operation, the cooling air supplied over the supply line 19, for instance at a temperature of approximately C., and distributed into the open space 14 passes with increased speed in a thin layer between the displacement body 36 and the inner and outer walls 9 and 20, respectively, toward the blade neck 6; the cooling air flowing along the outer wall 20 being directed by means of the bores 38 in the displacement body leg toward the blade neck 6. The cooling air is then subdivided into two halves between the cooling ribs 23 by means ofthe passage duct defined by the milled section 35 of the first rib and passes tangentially around the opposite sides of the blade neck 6. Opposite the input point at the first cooling rib 23, the two halves of coolant flow join together and pass through the passage duct defined by the milled section 35 of the second cooling rib 23. Following passage through this second milled section 35, the cooling air separates again into two halves and flows in this manner tangentially between the second and third ribs of the blade neck. After leaving the intermediary space bordering the last rib, the air passes on through the bores 39 of the sleeve 30 into the space surrounding these bores and flows then through ducts (not shown) into the flow passage of the work medium within the blade carrier 1.

As a result of the structural design described and the guidance of the cooling air, the bearing points of the blades, in particular the bearing 10 situated closest to the blade carrier 1 and, hence, to the flow of the work medium, can be kept at a temperature capable of insuring trouble-free operation.

The cooling gas also acts simultaneously as a blocking gas for the axle housing 4 in view of the fact that its pressure must always be greater than the pressure of the working medium in the rotor space. This prevents the penetrating of working medium or residues thereof into the axle housing 4 and, as a result of impurities or foreign substance that are carried along, in particular upon running in of the engine, the soiling of the bearing surfaces of the axle journal 8. In addition, because of the seal 55, the space between the inner wall 9 and the axle journal 8 is sealed off with respect to the space surrounding the blade carrier 1 so that even in the case of a possible over pressure of the working medium, the working medium is prevented from passing through along the bearing surfaces.

During some phases of operation of the turboengine, the part 5 contacted by the working medium can have a temperature up to 600 C. and more. As a result, a flow of heat can be produced over the blade neck 6, the blade journal 7, the axle journal 8, and the bearings 10, 11 against areas of a lower temperature at the outside of the engine. However, this heat flow is substantially reduced ahead of the bearing 10 as a considerable amount of heat is drawn off by the cooling air at the cooling ribs 23 before the heat reaches the blade journal 8. An additional heat transmission loss of the heat flow can be achieved by reducing the cross-section of the blade journal 8 and blade neck 6 by means of a central bore 40 in the blade and, as a result, the conduction crosssection of the heat flow.

Further, during operation, the bearing sleeve 10 is cooled from the outside by means of the cooling air passing along at the free end of the inner wall 9. At the same time, the part of the cooling air passing along the inner side of the outer wall reduces the influx of heat from the blade carrier 1 through the outer wall 20 onto the supports 12, 13 of the inner wall 9 and hence to the bearing sleeves 10, 11.

The combination of these above provisions guarantees a temperature for the bearings 10, 11, that is, below 200 C. and thereby removes the risk of the occurrence of trouble.

Referring to FIG. 5, the blade can alternatively be manufactured integrally as a compound casting element, a metallurgical connection being produced between the blade part 5 contacted by the work medium and the axle journal 8 in the area of the blade neck 6, for instance at the point 41 as shown. As above, the blade part 5 is made of a heat resistant material while the axle journal part 8 is made of a material suitable for dry operation. At the connection point 41 of these parts, an alloy is produced along a short stretch of the two different parts so that, after completion of the cast element, the blade appears as a single workpiece that can be machined. The compound casting is arranged in such a way that the alloy site is at a point at which at least the work medium cannot supply any additional heat to the; blade and, conversely, at which the blade is not yet fitted in a bearing.

Especially in the case of blades manufactured as compound castings, and also in the case of blades in which the two difierent materials have been interconnected mechanically by forcing or shrinking onto one another, it may be preferable to directly cool at least the bearing 10 of the axle journal 8 situated closest to the passage of the work medium. To this end, the axle journal 8 is reduced in diameter at the point 42 and a bearing tube 43 is slid over the reduced portion and welded to the axle journal 8 to form a hollow space 44 and receive the bearing sleeve 10. This hollow space 44 is connected by bores 45 in the journal 8 to the space 46 surrounding the blade neck 6 and, in addition, by means of radial bores 47 in the journal 8 with a central bore 40 in the journal 8. The central bore 40 leads into the open so that a partial amount of the flow of coolant determined by a dosing bore is diverted in the space 46 and guided through the hollow space 44. As a result, the bearing tube 43 and the plastic bearing 10 fitted thereon are efficiently cooled.

Referring to FIG. 6, the expansion pipes 17 can be of a length that is greater than the spacing between adjoining housings 4. That is, the expansion pipes 17 can be installed between the bearing housings 4 by means of a suitable tool and be then expanded against the housings 4. The expansion tubes 17 are thus urged elastically against the openings 48 of the axle housings 4 and are also pressed against the openings 48 as a result of internal pressure. In order to facilitate gripping and compression by a special tool, connecting flanges 49 are connected to the ends of the expansion pipes 17 and are preferably provided with collars 50 to form gripping surfaces.

What is claimed is:

1. A blade for a turboengine having a multi-part construction, one of said parts being of a heat resisting material for contacting a working medium in the turboengine and another of said parts being of a material capable of dry operation in a heat resistant plastic bearing without a lubricant supply to function as an axle journal wherein said one part and said axle journal part are integrally joined to each other as a compound casting element.

2. A blade as set forth in claim 1 which further includes a neck between said one part and said axle journal part for removing heat from said blade, said neck having a plurality of cooling ribs thereon.

3. A blade as set forth in claim 2 which further includes a cylindrical sleeve mounted on said cooling ribs about said neck, and a plurality of passage ducts disposed in spaced alternating manner in said ribs, each passage duct being disposed between said sleeve and a respective one of said cooling ribs whereby a cooling medium flowing between said sleeve and neck is directed tangentially about said neck between each pair of said ribs.

References Cited UNITED STATES PATENTS 1,047,379 12/1912 Bush l6495 1,444,213 2/1923 Shee l6495 2,648,519 8/1953 Campini 253-3915 2,708,564 5/1955 Erickson 25339.l5 2,950,084 8/1960 Perry 25339.1 3,079,128 2/1963 Burge 25378 HENRY F. RADUAZO, Primary Examiner 

